1. Field of the Invention
The present invention relates to an optical measurement apparatus for living body, in particular, an optical measurement apparatus for living body having an improved function of evaluating whether the settings of respective optical fiber probes of a probe device, which is attached to an inspection area of a subject, are adequate and which permits to evaluate correctly whether the settings of the respective optical fibers on a body surface of the subject, and a method thereof.
2. Description of the Related Art
An optical measurement apparatus for living body is an apparatus which permits to measure simply and easily living body information inside a living body, for example, such as blood circulation, hemodynamics and variation of hemoglobin concentration with low restriction to a subject and in a non-invasive manner to the living body through irradiating light having frequencies of from visible to near infrared regions to the living body and detecting the light penetrating through inside the living body.
When performing an optical measurement for living body of a subject representing a living body with the optical measurement apparatus for living body, at first an optical fiber probe device including irradiation use optical fiber probes and light receiving use optical fiber probes which are arranged alternatively at respective lattice points of, for example, 4×4 is attached on an inspection area of the subject, for example, on the headportion. In the case of the optical fiber probe device including irradiation use optical fiber probes and light receiving use optical fiber probes which are arranged alternatively at respective lattice points of 4×4, a total of 24 measurement channels each including a measurement point between respective adjacent irradiation use optical fiber probes and light receiving use optical fiber probes are formed inside the living body of the subject.
FIGS. 2˜5 are diagrams showing schematically four manners of settings of mutually adjacent irradiation use optical fiber and light receiving use optical fiber which are set on a body surface of a living body representing a subject and between which a measurement channel including a measurement point is formed.
FIG. 2 is an example where the setting of the optical fibers is adequate and shows a state in which inspection light 203 irradiated from irradiation use optical fiber 201 passes through inside of living body 205 and light 204 emerged outside from the living body makes incident into light receiving use optical fiber 202. Under this optical fiber setting condition, a sufficient near infrared light, which is subjected to absorption and reflection by hemoglobin inside the living body can be detected.
FIG. 3 is an example where the setting of the irradiation use optical fiber is inadequate and shows a state in which inspection light 303 irradiated from an irradiation use optical fiber 301 passes through an obstacle 306 such as hair, light 307 of which intensity is weakened passes through inside living body 305 and penetrating light 304 emerged outside from the living body makes incident into light receiving use optical fiber 302. Under this optical fiber setting condition, since signals of the irradiation light 303 are disturbed by the obstacle 306, sufficient near infrared light subjected to absorption and reflection by hemoglobin inside the living body 305 can not be detected. Further, even in a case when no obstacle 306 such as hair is caught between the irradiation use optical fiber 301 and the surface of the living body, if the irradiation use optical fiber 301 is remote from the surface of the living body and the attenuation of the irradiation light is extreme, since sufficient inspection light which has penetrated through the subject can not be detected, the setting of the optical fiber is evaluated as inadequate.
FIG. 4 is an example where the setting of the light receiving use optical fiber is inadequate and shows a state in which irradiation light 403 irradiated from an irradiation use optical fiber 401 passes through inside living body 405 and penetrating light 404 emerged outside from the living body passes through an obstacle 406 such as hair, light 407 of which intensity is weakened makes incident into light receiving use optical fiber 402. Under this optical fiber setting condition, since signals of the penetrating light 404 are disturbed by the obstacle 406, sufficient near infrared light subjected to absorption and reflection by hemoglobin inside the living body 405 can not be detected. Further, even in a case when no obstacle 406 such as hair is caught between the light receiving use optical fiber 401 and the surface of the living body, if the light receiving use optical fiber 402 is remote from the surface of the living body and the attenuation of the irradiation light is extreme, since sufficient inspection light which has penetrated through the subject can not be detected, the setting of the optical fiber is evaluated as inadequate.
FIG. 5 is an example where the setting of both irradiation use and light receiving use optical fibers is inadequate because both are inadequately remote from a living body representing a measurement object and shows a state in which since irradiation use optical fiber 501 is remote from a living body, irradiation light 503 of which intensity is weakened passes through inside living body 505 and penetrating light emerged outside from the living body of which intensity is weakened makes incident into light receiving use optical fiber 502. On the other hand, since the light receiving use optical fiber 502 is also remote from the surface of the living body, light from the irradiation use optical fiber 501 of which intensity is high in comparison with that of the light passed through inside the living body is directly makes incident to the light receiving use optical fiber 502. Under this condition, since the penetrating light 504 passed through inside the living body 505 mixes with the direct light 506 from outside the living body, the amount of received light is much, however, sufficient near infrared light which is subjected to absorption and reflection by hemoglobin inside the living body 505 representing measurement object can not be detected.
In a conventional optical measurement apparatus for living body as, for example, disclosed in JP-A-11-311599, an evaluation and judgment is performed whether the setting of respective pairs of adjacent optical fibers each constituting a measurement channel of a probe device which is attached on a body surface of an inspection area of a subject is adequate or not in such a manner that after setting the respective optical fibers, a short time preparatory measurement is performed prior to beginning an actual measurement, in which gains of irradiation light amount from respective irradiation use optical fibers and received light amount of respective paired light receiving use optical fibers are detected, more specifically, a gain adjustment is performed for the respective measurement channels and for a measurement channel of which gain adjustment has failed the setting of the optical fibers is evaluated and judged as inadequate and resetting work of the optical fibers is performed for the respective concerned channels.
However, with the method as disclosed in the conventional optical measurement apparatus for living body, the inadequate optical fiber setting state as shown in FIG. 5 was evaluated and judged as adequate optical fiber setting because the amount of light received by the light receiving use optical fiber is sufficient, although the amount of light penetrated inside the living body containing hemoglobin signals is insufficient.
For this reason, even though the measurement data of such measurement channels is erroneous measurement data, the erroneous measurement data are treated as correct measurement data, operated and processed, of which result possibly causes an erroneous diagnosis or reduction of diagnosis efficiency.
An object of the present invention is to provide an optical measurement apparatus for living body having a function which performs a correct evaluation and judgment whether the setting of respective pairs of adjacent optical fibers each constituting a measurement channel of a probe device which is attached on a body surface in an inspection area of a subject is adequate or not and a method thereof.
Another object of the present invention is to provide an optical measurement apparatus for living body, which can prevent an erroneous diagnosis or reduction of diagnosis efficiency due to an inadequate setting of respective pairs of adjacent optical fibers each constituting a measurement channel of a probe device which is attached on a body surface in an inspection area of a subject and a method thereof.